This proposal concerns the genetic analysis of influenza A, B and C viruses. 1.) We will clone and sequence several NP and M genes of influenza A viruses, the HA, NP, NA, M and NS genes of influenza B viruses and the corresponding genes of influenza C viruses. 2.) We will attempt to express cloned influenza virus genes in eucaryotic cells using SV40 and retrovirus vector systems. These experiments are designed to study the function of individual genes and regions of the genes. Cells constitutively expressing influenza virus polypeptides should, via complementation, permit the isolation of specific viral mutants. Furthermore, we will attempt to establish a system which permits the rescue of RNA from cloned DNA into virus particles. 3.) We will continue our studies on the characterization of influenza virus polypeptides, including analysis of the M2 polypeptide of influenza A viruses. We will also explore the possibility that open reading frames on the negative strand of some influenza virus NS genes direct the synthesis of a viral polypeptide in vivo. We will also establish a genetic map for influenza C viruses.